The long-range objective of this research project is to understand the behavioral impairments and the neural mechanisms that give rise to the characteristic social abnormalities in autism. Autism is characterized by many deficits;the most distinctive of the abnormalities is in reciprocal social interactions, others being impairments in verbal and non-verbal communication and a restricted range of interests and activities. Deficits in social behavior may exert profound and pervasive effects across other domains of functioning, and over the course of development, especially since early learning experiences are mediated to a great extent through social interactions. Educators, parents, and clinicians often report that social interactions appear to be far less rewarding for autistic children compared to typically developing (TD) children. The long-term goal of this research program is to understand the reward system in the autistic brain. The Specific Aims of this R21 Exploratory/Developmental project are: (1) To examine whether children with high functioning autism (HFA) differ from TD children in terms of their preference for social activities versus non-social activities. (2) To demonstrate that relative preference rankings correspond to reinforcer efficacy within and across groups (HFA/TD) and classes of stimuli (social/non-social), i.e., that reinforcer efficacy is the operational definition of a reward. (3) To demonstrate in TD children, that established reinforcers, whether they are social stimuli or non-social stimuli will activate the brain's reward system (nucleus accumbens, amygdala, orbital frontal). (4) To perform a pilot study to test the hypothesis that neural activation in children with HFA is equal to TD children for non-social activities but not for social activities. These studies will 1) standardize the behavioral protocol;2) define the baseline behavioral parameters in TD children and in children with HFA;and 3) lay the groundwork for using fMRI in TD and HFA children. This will enable us to ultimately be able to characterize and contrast behavioral patterns, brain-behavior relationships, and neurologic function of the reward system in the two groups. The results will help us to determine whether some of the social deficits present in HFA may be associated with differences from TD in the neural reward system and thereby expand our understanding of the underlying mechanisms of autism. PUBLIC HEALTH RELEVANCE: This study is designed to develop the protocols that will allow us to determine whether children with HFA differ from TD children with regard to the reinforcing value of social versus non-social stimuli, the functioning of the reward system in general, and whether there are differences in how the reward system is activated in response to social stimuli in particular. The results will help us to determine whether some of the social deficits present in HFA may be associated with differences (from TD) in the neural reward system and thereby expand our understanding of the underlying mechanisms of autism. The conclusions from the proposed studies may lead to improved interventions for the treatment of autistic children.